The present invention relates to a reduced cost electrical apparatus having parametrizable function.
A large number of electrical apparatuses possess a parametrizable function, this signifying that the user of the apparatus can allocate to a parameter a value chosen from among several possible values and that the apparatus takes this value into account in its operation. The apparatus then generally has one or more actuation members which the user can move in such a way as to make it take a discrete position chosen from several positions. The actuation member can be a control button with rotary or linear movement, which can be actuated manually, either directly or, for buttons of very small size, by way of a small screwdriver; the control button is accessible to the user from outside the shroud of the apparatus and the various discrete positions which it can take are labelled on the shroud of the apparatus.
For example, in a timer, the parametrizable functions may be the duration of the timing or an operational mode. The range of values for the timing can, for example, lie between 0.06 seconds and 30 hours. The operational mode relates to the operation of the relay or relays which the timer contains. Several operational modes exist and amongst the most widely used are delayed switch-on or the complementary thereof. In the first mode, the timing begins when the timer is switched on and the relay changes state at the end of timing and in the second mode, the relay changes state at switch-on and retains this state throughout the duration of the timing before reverting to its original state at the end of timing.
The allocating of a value to a parameter is achieved either by virtue of a switch with several positions, so as to define for example an operational mode or a range of values of a parameter (range of durations for a timer), or by way of a potentiometer with fine adjustment so as to define an accurate value of a parameter (adjustment of duration within the chosen range).
For example, one can imagine a timer with three operational modes, six ranges of durations, and fine adjustment within each range of duration. Such a timer is represented in FIG. 1 (referenced 10). If it were constructed according to the principles of the known technique, its front face would carry three control buttons:
the upper button 12 would actuate a switch with three positions making it possible to chose one of three possible modes of operation labelled by the letters A, B and C;
the central button 14 would actuate a switch with six positions making it possible to define six possible ranges of duration, labelled on the box by indications representing (for example) the maximum value of duration possible for each range;
the lower button 16 would actuate a fine-adjustment potentiometer, graduated from 1 to 10 (for example), allowing continuous adjustment of the duration within the range selected by the button 14.
The orifices 18 at the base of the front face of the timer allow access to screws for binding electrical wires via which the timer can be connected to an electrical installation in which it achieves its function.
The switches which select the ranges of parameters or the operational modes may be expensive, especially if they must possess a considerable number of positions. They are in general devised so as to provide directly in binary form a digital signal controlling the electronic circuits which serve to establish the operation of the timer. A switch having a number of positions N which is strictly less than 2p provides a digital signal of p bits. The larger N is, the larger p must be and the more expensive is the switch.
This is all the more true if the switches have to be miniaturized. Typically, the width of the timer represented in FIG. 1 could be less than 2 centimetres, and the control buttons 12, 14, and 16, as well as the switches and potentiometer which are behind the buttons, do not exceed one centimetre in diameter.
On the other hand, the larger the number N of positions of the switch, the more expensive the electronic circuit (microcontroller type) which ensures the operation of the apparatus is liable to be, owing to the fact that this circuit must possess p inputs reserved for the link with the switch.
The invention aims to diminish these drawbacks while contriving matters such that the user has a practically unchanged perception of the operation of the apparatus.
To accomplish this, the present invention proposes an electrical apparatus having at least one parametrizable function, characterized in that it comprises at least one potentiometer having an actuation member, cooperating with notched indexation means, these indexation means demarcating several discrete positions of the actuation member, each position corresponding to a desired value of a parameter, means of analogue/digital conversion and interpretation receiving an analogue voltage delivered by the potentiometer, dependent on the discrete position taken by the actuation member and delivering a digital signal representative of the position of the actuation member and hence of the desired value of the parameter, this digital signal serving as parametrization control signal for the apparatus.
Thus, according to the invention, the switch for selecting parameter, range of parameters, or operational mode, is physically replaced by an indexation potentiometer. This potentiometer, supplied with a voltage, delivers an analogue signal, and it is within the electronics of the apparatus that this signal is converted into a digital value (that which in the prior art was delivered by a switch) representing the index on which the actuation member of the potentiometer is positioned. Hence, the variation in the resistance of the potentiometer is harnessed in order to determine the indexed position on which the actuation member has been placed. It will be noted that the analogue/digital conversion can form part of the microcontroller which manages the entire operation of the apparatus, so that a single microcontroller input is then required to achieve the link with the potentiometer regardless of the number N of indexed positions which may be taken by the actuation member of the potentiometer.
The potentiometer, even when provided with notched indexation means, is less expensive than a switch once the number of indexed positions exceeds 3 or 4.
The user does not perceive any difference relative to the apparatuses which he customarily knows: the control buttons remain identical and the marking of the positions can remain unchanged; the sensation of turning a switch remains present by virtue of the notches of the indexation means.
If the potentiometer is sufficiently accurate and linear, and if it is supplied with a sufficiently accurate voltage, the means of analogue/digital conversion and interpretation may comprise a straightforward analogue/digital converter which receives the analogue voltage and which delivers directly the digital signal representative of the position of the actuation member.
If the potentiometer is nearer the bottom of the range, and in particular if it is not linear or not sufficiently linear (whereas one wishes to distribute the indexed positions very regularly), the means of analogue/digital conversion and interpretation may comprise not only an analogue/digital converter which receives the analogue voltage and which delivers an intermediate digital signal which directly represents the position of a slider of the potentiometer, but also a decoding device which receives this intermediate digital signal and which transposes it into a digital signal representative of one actuation member position from among N indexed positions. In this case, it will be understood that the intermediate digital signal can comprise m bits, with m greater than the number p of bits defining one from among N positions.
To simplify the construction, one may envisage the notched indexation means as forming part of the potentiometer.
To diminish the consequences of the uncertainty in the exact position of the slider with respect to the resistive track, it is possible for the resistive track to take the form of discontinuous resistive lands separated by conductive lands.
If the apparatus comprises several potentiometers, it is preferable to provide a multiplexer inserted between the potentiometers and the means of analogue/digital conversion and interpretation, thereby making it possible to avoid increasing the number of analogue/digital converters.
From the mechanical point of view, the indexation means can comprise a first indexation means integral with the actuation member and a second indexation means carried by a shroud of the apparatus.
In order for the switching from one discrete position to another to occur in a crisp and reliable manner, it is preferable for the cooperation between the indexation means to be of elastic type, that is to say that a certain restoring force compels the actuation member to stabilize on one of the indexed positions, without resting between two positions.
One of the two indexation means can comprise at least one lug and the second indexation means several notches, the lug becoming housed in one of the notches. Or conversely, there are several lugs and one notch, the notch becoming applied to one of the lugs.